A teenage girl was killed and 44 passengers needed to be treated in hospital when a coach taking schoolchildren to the Alton Towers amusement park crashed in "horrendous" weather conditions in south-west Scotland today.

Natasha Paton was one of a group of 39 sixth year pupils from Lanark Grammar school who had just left the town for the school's annual Easter visit to Alton Towers, in Staffordshire, when their coach crashed in a blizzard before dawn.

The 17-year-old was killed when the coach plunged into a river after crashing through a bridge parapet as it negotiated a sharp bend on the A73, south-west of Biggar, shortly before 6am.

The coach fell 10ft (3.5 metres), throwing her through a window as it rolled over and crushing her.

Tonight the teenager's parents issued a statement: "We are devastated at the loss of our beloved daughter. Natasha was a typical teenager and very popular with lots of friends and will be greatly missed by all who knew her."

Two other passengers were airlifted by Royal Navy helicopter to the Southern General hospital, in Glasgow, with serious chest and leg injuries. The driver had to be cut free from the vehicle, sustaining a broken leg and cuts. Almost all the pupils and staff on board needed treatment for cuts, bruises and shock.

It quickly emerged that lorry drivers, motorists and local residents had helped the injured and distressed passengers. Lorry drivers used their cabs to shelter some children, while residents in the nearby village of Wiston opened the village hall as a temporary refuge.

Mark Atwood, who lives close to the crash scene, said he had taken in two children soon after the accident. "They were visibly shaken, tearful and very emotionally upset," he said.

Iain Heggison, another nearby resident, heard the crash and found the bus on its side. "It was packed with kids. They were crying and hysterical. It was horrible," he said. "I thought I was dreaming but this is a nightmare, total nightmare."

Rescue workers got passengers out of the bus through skylights and broken windows in driving winds and heavy snow.

By lunchtime, 25 had been allowed to go home, while 19 remained in hospitals around Lanarkshire and Glasgow.

One parent was highly critical of the decision to leave Lanark under those conditions. Susan Thornton, a driving instructor, told the BBC she had stopped her son Adam from taking the trip after driving through severe weather last night.

"I wish somebody had had the sense to make a decision not to drive in that," she said. "I do despair of any coach company which would have a driver who would take 39 children in that weather ... it's just not the weather to be out on the roads at all."

Alan Purdie, the owner of the coach operator involved, Photoflash, said the firm was "distraught". He told Radio Clyde he believed black ice was to blame, adding: "It is a tragedy. We are all deeply concerned for the parents [of the victim] this morning. The main roads had snow on them but were not that bad. But there was black ice under the snow on that road."

Alex Salmond, the first minister of Scotland, and prime minister Gordon Brown, expressed their sadness at the tragedy.

Salmond said: "Our thoughts are very much with the parents and relatives and staff members caught up in this incident."

The accident was the most serious of a number of crashes across Scotland as blizzards, high winds and heavy rain hit much of the country, leading to treacherous conditions. In south-west and north-eastern Scotland, about 31,000 homes were left without electricity, while major roads including the A9, A1, A68 and A96 were closed by heavy snow, with motorists left stranded.